1. Calculate Decile deviation, Coefficient of D.D., Interdecile range from the following grouped data

X	Frequency
0	1
1	5
2	10
3	6
4	3

Solution:
Decile deviation :

`x`	Frequency `f`	`cf`
0	1	1
1	5	6
2	10	16
3	6	22
4	3	25
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	`n = 25`	--

Here, `n = 25`

`D_1 = ((n+1)/10)^(th)` value of the observation

`=(26/10)^(th)` value of the observation

`=(2.6)^(th)` value of the observation

`=1`

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`D_9 = ((9(n+1))/10)^(th)` value of the observation

`=((9*26)/10)^(th)` value of the observation

`=(23.4)^(th)` value of the observation

`=4`

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InterDecile range `=D_9 - D_1=4-1=3`

Decile deviation `=(D_9 - D_1)/2=(4-1)/2=3/2=1.5` (Semi-InterDecile range)

Coefficient of Decile deviation `=(D_9 - D_1)/(D_9 + D_1)=(4-1)/(4+1)=3/5=0.6`

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